The focus of the EARLYDRAIN study is to examine the efficacy of application of lumbar drainage in patients with acute subarachnoidal hemorrhage from a cerebral aneurysm. Hypothesis is that early application of lumbar drainage after aneurysmal SAH leads to a diminished incidence of cerebral vasospasm, as assessed by digital subtraction angiography, and an improved outcome, measured by the modified Rankin score, at six months.